1. Field
This application relates generally to wireless communication and more specifically, but not exclusively, to improving wireless mobility.
2. Introduction
A wireless communication network is deployed over a defined geographical area to provide various types of services (e.g., voice, data, multimedia services, etc.) to users within that geographical area. In a typical implementation, access points (e.g., corresponding to different cells or sectors) are distributed throughout a network to provide wireless connectivity for access terminals (e.g., cell phones) that are operating within the geographical area served by the network. In general, at a given point in time, the access terminal will be served by a given one of these access points. As the access terminal roams throughout this geographical area, the access terminal may move away from its serving access point and move closer to another access point. In this case, the access terminal may be handed-over from its serving access point to be served by the other access point to maintain mobility for the access terminal.
An example of how an access terminal may be handed-over follows. The access terminal may regularly perform radio frequency (“RF”) measurements and determine that the signals being received from a neighbor access point (e.g., a so-called target access point) are stronger than the signals being received from the current serving access point by a certain margin. As a result, the access terminal sends a measurement report with this information to the network (e.g., to the serving access point). The serving access point (i.e., the source access point for the handover) then performs backhaul communication with the target access point to negotiate resources for the access terminal on the target access point. Here, the serving access point may send context information for the access terminal to the target access point. In addition, the serving access point sends a handover command to the access terminal, wherein the handover command identifies the resources assigned to the access terminal on the target access point. The access terminal may then connect to the target access point using these resources.
Under certain circumstances, radio conditions between an access terminal and its serving access point may deteriorate to the point where the access terminal experiences radio link failure with the serving access point. In such a case, after the access terminal declares radio link failure, the access terminal may attempt to access a target access point. During this access the access terminal provides its own identification and the identity of the prior serving access point to the target access point. In the event the target access point was prepared for the handover by the serving access point (e.g., as discussed above), the target access point may be able to serve the access terminal since the target access terminal may have context information and other data for the access terminal. On the other hand, if the target access point had not been prepared, the target access point may reject the access terminal whereupon the access terminal may go to idle mode. Alternatively, the target access point may perform a forward handover procedure, whereby the target access point fetches the context information for the access terminal from the prior serving access point.